In the field of open-heart surgery, the use of prosthetic valve devices is well known in the art, and varying forms of such valves are employed for replacement of the aortic valve, the mitral valve, and others.
In thus implanting a prosthetic device in a living body, it is necessary to satisfy several requirements. Thus the valve must, of necessity, be capable of operating continuously for relatively long periods of time without excessive wear or malfunction. Passage of blood through the valve must be carried out in such a way that traumatic effects are avoided and red blood cells are not broken down into white cells. Still further, any condition which may induce the occurrence of blood clotting has to be carefully avoided, and there must be freedom from turbulence or flutter or other condition which would cause patient discomfort.
In one early form of valve structure, a ball valve is used in which a ball member is loosely contained in a supporting cage. It has been found that this device is unsatisfactory in that the ball member, in its cage, presents an objectionably high profile, and the ball, in returning to its seat in the cage, tends to break down red cells to a troublesome degree. Such valves are used very little at the present time.
Another form of valve presently being utilized is a disc valve. With this valve in an open position, flow of blood shoots out in an angular path, tending to create undesirable turbulence, and there is also a tendency for blood to flow behind the valve in an objectionable manner.
Various other valve structures are described in Vol. 154, American Surgery, page 726, 1961.
A number of other valve structures are disclosed in recently issued patents including U.S. Pat. Nos. 3,312,237; 3,800,403; 3,861,416; and 3,116,562.
All of the valve structures disclosed in these patents are, so far as we are aware, incapable of satisfying all of the requirements noted above, and there continues to be a need for a more satisfactory valve means of the class indicated.